The present invention relates generally to a system for checking the condition or quality of adhesive application on an automatic merchandize packaging line.
On the automatic merchandize packaging line thermal adhesive is applied to the flaps of the packages, mainly made of cardboard, spot by spot by means of a gun or the like. The deposit of adhesive in each spot form a bead so that as a whole a plurality of beads are aligned along the edges of tile flaps of packages. In this way the flaps of the packages are heat sealed. However, a problem arises in automatically applying adhesive on-the flaps spot by spot in that the amount of applied adhesive tends to be irregular from bead to bead, in some beads short and others excessive. When the amount is short, it results in poor bond between the flaps. When it is excessive, it causes smearing and stains the packages. What is worse, smeared adhesive causes the packages to stick to other objects. Therefore, constant care must be taken to check the condition or quality of beads on the flaps of packages.
In order to monitor, a photoelectric switch is proposed for being placed along the operation line to find any poor or improper beads. However, the monitoring results are subject to photoelectricity whose intensity depends upon the nature and quality of the cardboard of which the packages are made, thereby failing to obtain precise data. As an alternative, a monitor camera is proposed whereby the condition of beads is visually inspected through a picture. However, the picture is not always clear, and in order to effect precise inspection, an expensive detector must be additionally equipped. Thus the cost is increased.
Another monitoring method is disclosed in the Japanese Publication (allowed) No. 4-51415, which is designed to find a defective bead by reference to temperatures of the beads. More specifically, it is ascertained whether or not each bead has adhesive and how many beads are formed, by counting signals from an infrared sensor for sensing the temperatures of the beads. However, this method is only to check the presence of adhesive in each spot but cannot inspect the condition or quality of adhesive application in each spot.